Equalization system for modems in a polled arrangement

Abstract

In a system in which a central modem individually polls a number of remotely located modems for data, an adaptive equalizer in the central modem is initially trained to minimize communication link interference from a remote modem and develops a set of equalizer coefficients based on the initial training which is transmitted to the remote modem and stored there for future use while the central modem goes on to do the same with other remote modems. When a remote modem is polled, the stored equalizer coefficients are used to set the adaptive equalizer of the remote modem so the adaptive equalizer of the central modem does not have to be retrained for each individual remote modem.

I claim: 
     
       1. In a data transmission system of the type including a central data transmitter-receiver linked to a plurality of remote data transmitter-receivers via separate data transmission channels, each channel having varying electrical characteristics, the central data transmitter-receiver including means for polling each of the data transmission channels, the system further comprising: an automatic equalizer at the central data transmitter-receiver;   and automatic equalizer at each of the remote data transmitter-receivers;   means at the central data transmitter-receiver for generating an initial training sequence of data signals, for transmitting the training sequence, in turn, over each data transmission channel, for detecting the electrical characteristics of each data transmission channel, generating equalization coefficients suitable for adjusting the characteristics of the data transmission channel in a preferred manner, and for transmitting as data the equalization coefficients associated with each data transmission channel to its associated remote data transmitter-receiver; and   means at each remote data transmitter-receiver for storing the transmitted equalization coefficients associated with its data transmission channel,   whereby each data transmission channel is automatically equalized by the qualizer associated with its respective remote date transmitter-receiver whenever the particular data transmission channel is polled by the central data transmitter-receiver.   
     
     
       2. The data transmission system of claim 1 wherein each said data transmitter-receiver is a modem. 
     
     
       3. In a data transmission system of the type including a central data transmitter-receiver linked to a plurality of remote data transmitter-receivers via separate data transmission channels, each channel having varying electrical characteristics, the central data transmitter-receiver including means for polling each of the data transmission channels, and each remote transmitter-receiver including automatic equalizer means, a method for equalizing the electrical characteristics of each of the data transmission channels, comprising the steps of: (a) generating an initial training sequence of data and transmitting this training sequence data over a data transmission channel;   (b) detecting at the central data transmitter-receiver the training sequence data and generating therefrom equalization coefficients characterizing the data transmission channel;   (c) transmitting as data the equalization coefficients characterizing the data transmission channel from the central data transmitter-receiver to the remote data transmitter-receiver;   (d) storing the transmitted equalization coefficients for the channel at the remote data receiver-transmitter;   (e) repeating steps (a)-(d) until all data transmission channels have had equalization coefficients generated and stored; and   (f) adjusting the equalization of each equalizer associated with each remote data transmitter-receiver in accordance with the stored equalization coefficients associated therewith whenever a remote data transmitter-receiver is polled by the central data transmitter-receiver.     
     
     
       4. The system of claim 3 further including the step of periodically repeating steps (a)-(e) between transmission of data over the data transmission channels. 
     
     
       5. The system of claim 3 wherein the step of generating an initial training sequence of data is performed at the central data transmitter-receiver, and each remote transmitter-receiver, in turn, receives the initial training sequence and retransmits it back to the central data receiver-transmitter.